Probing water compartments and membrane permeability in plant cells by 1H NMR relaxation measurements

摘要

¹H NMR relaxation times (T1 and T2) in parenchyma tissue of apple can identify three populations of water with different relaxation characteristics. By following the uptake of Mn²⁺ ions in the tissue it is shown that the observed relaxation times originate from particular water compartments: the vacuole, the cytoplasm, and the cell wall/extracellular space.Proton exchange between these compartments is controlled by the plasmalemma and tonoplast membranes. During the Mn²⁺ penetration experiment, conditions occur that cause the relaxation times of protons of cytoplasmic water to be much shorter than their residence time in the cytoplasm. Then the tonoplast permeability coefficient Pd for water can be calculated from the vacuolar T1 and T2 values to be 2.44 10^-5 m·s^-1.